Tea and Foods Rich in Theanine

Are There Any Foods Rich in Theanine?

Are There Any Foods Rich in Theanine?
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Updated on July 31, 2025
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If you tend to hit a midday slump, you may want to trade your coffee break for an afternoon tea. L-theanine, an amino acid known for its soothing effect and potential to improve concentration, is abundant in tea, though finding food sources is a tough task.

 Read on to learn about L-theanine’s potential benefits and the best ways to take it.

Benefits of Theanine

Drinking a glass of green tea may come with a number of benefits, thanks to theanine.

“Theanine is an amino acid that may help calm you down, reduce stress and anxiety, and improve attention, focus, memory, and learning,” says Karen Kjaerulff, RDN, a dietitian in Delray Beach, Florida.

The reason has to do with how L-theanine interacts with brain chemicals called neurotransmitters.

 The amino acid increases levels of GABA, serotonin, and dopamine, which signal the brain to help regulate your mood and concentration, says Diana Orchant, RDN, a dietitian in New York City. It’s chemically similar to GABA and glutamate, which help transmit nerve impulses to the brain.

When it comes to using theanine supplements for anxiety, more studies and research are needed on the topic.

 Some studies suggest it can help reduce anxiety, including in people with generalized anxiety disorder.

 However, other studies indicate it has no or little effect.
Theanine may also improve sleep quality, although larger, more well-designed trials are needed, says Uma Naidoo, MD, director of nutritional and lifestyle psychiatry at Massachusetts General Hospital in Boston and a Harvard Medical School faculty member.

In a 2025 review in Nutrition Research, researchers recognized L-theanine as a compound with potential medical value, yet pointed out that rigorous clinical research in humans is lacking.

Foods Highest in L-Theanine

While some teas are rich in theanine and it’s available in supplement form, it’s not abundant in food sources. Here are the most common food sources of L-theanine.

Tea

While green tea tends to contain the most theanine, other tea varieties also have high levels of the amino acid.

All tea comes from the same plant, Camellia sinensis, says Jaime Gnau, RDN, a clinical assistant professor in the department of public health and sports medicine at Missouri State University in Springfield, but how the leaves are processed determines different types of tea.

 Typically, 2 to 3 grams (g) of loose tea leaves are recommended to brew an 8-ounce (oz) cup of tea, she says.
Here’s the average content of L-theanine in different types of tea, according to a review in Frontiers in Nutrition:

 
  • Green tea: 6.56 milligrams per gram (mg/g)
  • White tea: 6.26 mg/g
  • Oolong tea: 6.09 mg/g
  • Black tea: 5.13 mg/g
“It’s important to note that L-theanine content in tea can vary widely due to preparation time and tea processing,” Gnau says.

 
Note: Herbal “teas” are not made from tea leaves and do not contain theanine, Kjaerulff says.

 These tend to be made from other plants, including ginger, chamomile, and peppermint.

Mushrooms

While tea is the richest source of L-theanine, some mushrooms, such as bay boletes, also contain small amounts.

 
As a water-soluble amino acid, theanine is absorbed through the intestines, and peak plasma concentrations occur about 50 to 60 minutes after eating, Gnau says.

 Peak plasma concentration means the highest level of a drug or supplement in your bloodstream.

Effective Ways to Get Theanine

The most effective way to get theanine in your diet is by drinking green tea, Dr. Naidoo reiterates. Just remember that green tea does contain caffeine.

 “Drinking a large amount of green tea can cause nausea, irritability, and an upset stomach because of the caffeine content,” Naidoo says.
If using oral supplements, be sure to look for labeling indicating third-party testing, such as by U.S. Pharmacopeia (USP), Gnau says.

 “This ensures the safety of the product since supplements are not regulated [like medications] by the Food and Drug Administration (FDA),” Gnau says.

 Always talk to your doctor before starting any new supplements.

The Takeaway

  • Some studies suggest that L-theanine may help reduce stress, improve sleep, and enhance concentration, among other benefits. However, more robust research on humans is needed.
  • Tea (especially green tea) is the richest source of L-theanine, though some mushrooms like bay boletes offer trace amounts of the amino acid.
  • If you’re considering taking an L-theanine supplement, consult your healthcare provider first. If you get the green light, select a product that’s been third-party tested because the FDA doesn’t regulate dietary supplements in the same way as medications.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Here’s What You Need to Know About L-Theanine. Cleveland Clinic. July 19, 2023.
  2. Wang L et al. How Does the Tea L-Theanine Buffer Stress and Anxiety. Food Science and Human Wellness. May 2022.
  3. Bulman A et al. The Effects of L-Theanine Consumption on Sleep Outcomes: A Systematic Review and Meta-Analysis. Sleep Medicine Reviews. June 2025.
  4. Dashwood R et al. L-Theanine: From Tea Leaf to Trending Supplement — Does the Science Match the Hype for Brain Health and Relaxation? Nutrition Research. February 2025.
  5. Godman H. Does Drinking Tea Really Help Health? Harvard Health Publishing. February 1, 2025.
  6. Li MY et al. L-Theanine: A Unique Functional Amino Acid in Tea (Camellia Sinensis L.) With Multiple Health Benefits and Food Applications. Frontiers in Nutrition. April 4, 2022.
  7. Tea. Harvard T.H. Chan School of Public Health. April 2023.
  8. Bloomer RJ et al. The Physiologic Benefits of Caffeine and L-Theanine. Acta Scientific Nutritional Health. June 7, 2024.
  9. How Green Tea Can Benefit Your Health. Cleveland Clinic. September 5, 2024.
  10. U.S. Pharmacopeia. The United States Pharmacopeial Convention.
  11. Dietary Supplements. U.S. Food and Drug Administration. October 1, 2024.
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Roxana Ehsani, RDN

Roxana Ehsani, RD

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Roxana Ehsani, RD, is a Miami-based licensed dietitian-nutritionist, board-certified specialist in sports dietetics, and media spokesperson, consultant, and content creator for food and nutrition brands. She is an adjunct instructor for sports nutrition at Virginia Tech in Blacksburg.

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